RESUMO
In this work, we report how manganese phthalocyanine (MnPc) films obtained using the ultrasonic spray-pyrolysis technique at 40 °C deposited on glass substrate subjected to thermal annealing at 100 °C and 120 °C. The MnPc films were characterized using UV/Vis spectroscopy, Raman spectroscopy, X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). The absorption spectra of the MnPc films were studied in a wavelength range from 200 to 850 nm, where the characteristic bands of a metallic phthalocyanine known as B and Q bands were observed in this range of the spectrum. The optical energy band (Eg) was calculated using the Tauc equation. It was found that, for these MnPc films, the Eg has the values of 4.41, 4.46, and 3.58 eV corresponded to when they were deposited, annealing at 100 °C and 120 °C, respectively. The Raman spectra of the films showed the characteristic vibrational modes of the MnPc films. In the X-Ray diffractograms of these films, the characteristic diffraction peaks of a metallic phthalocyanine are observed, presenting a monoclinic phase. The SEM images of these films were studied in a cross-section obtaining thicknesses of 2 µm for the deposited film and 1.2 µm and 0.3 µm for the annealed films at 100 °C and 120 °C. Additionally, in the SEM images of these films, average particle sizes ranging from 4 to 0.041 µm were obtained. The results agree with those reported in the literature for MnPc films deposited by performing other techniques.
RESUMO
Silver and gold nanoparticles were synthesized under environmentally-friendly reaction conditions by using a biodegradable copolymer and water as a solvent. The triblock copolymer Pluronic P103 was utilized as a stabilizing agent or soft template to produce Ag and Au nanoparticles (NPs) of different sizes. Moreover, in the synthesis of Au NPs, the polymer acted as a reducing agent, decreasing the number of reagents used and consequently the residues produced, hence, rendering the procedure less complicated. It was observed that as the concentration of the polymer increased, the size of the metallic NPs augmented as well. However, AgNPs and AuNPs prepared with 1 and 10 wt% Pluronic P103, respectively, showed a significant decrease in particle size due to the presence of polymeric soft templates. The hybrid materials (metal/polymer) were characterized by UV-Vis spectroscopy, DLS, and TEM. The pre-synthesized nanoparticles were employed to decorate anatase-TiO2, and the composites were characterized by DRS, XRD, BET surface area measurements, the TEM technique with the EDS spectrum, and XPS spectroscopy to demonstrate NPs superficial incorporation. Finally, methylene blue was used as a probe molecule to evidence the effect of NPs decoration in its photocatalytic degradation. The results showed that the presence of the NPs positively affected methylene blue degradation, achieving 96% and 97% removal by utilizing TAg0.1 and TAu10, respectively, in comparison to bare anatase-TiO2 (77%).
RESUMO
The search for novel materials and the development of improved processes for water purification have attracted the interest of researchers worldwide and the use of titanium dioxide in photocatalytic processes for the degradation of organic pollutants contained in water has been one of the benchmarks. Compared to crystalline titanium dioxide (cTiO2), the amorphous material has the advantages of having a higher adsorption capacity and being easier to dope with metal and non-metal elements. In this work, we take advantage of these two features to improve its photocatalytic properties in the degradation of Rhodamine B. The structural characterization by XRD analysis gives evidence of its amorphous nature and the SEM micrographs portray the disc morphology of 300 nm in diameter with heterogeneous grain boundaries. The degradation of Rhodamine B tests with the amorphous TiO2 using visible light confirm its improved catalytic activity compared to that of a commercial product, Degussa P25, which is a well-known crystalline material.
